A speaker includes a voice coil plate and a diaphragm interposed between magnets, and the diaphragm is vibrated by movements of the voice coil plate, thereby generating sounds.
The voice coil plate used in the flat-type speaker is wound on a single side or on both sides of a plate-type coil base into an oval shape or pattern-printed.
When an electric current flows through the voice coil of the voice coil plate, the flowing current generates a magnetic field that is expanded and contracted in the same frequency as an audio signal around the voice coil. Since a magnetic field generated from the magnets within a speaker unit is applied to the voice coil, the magnetic field generated from the magnets interacts with the magnetic field generated from the voice coil and thus the voice coil plate moves up and down. Since the voice coil plate is connected to the diaphragm of the speaker unit, the diaphragm moves up and down and pushes air, with the result that sounds are generated by the vibration of the air.
Such a flat-type speaker has been developed to have a gradually slim size and long structure along with an increase of an output capacity. Furthermore, in order to increase the output capacity of the flat-type speaker, the development of a flat-type speaker configured to have a plurality of magnetic circuits combined is gaining strength as an important problem.